From 8301f87815fe6b4b1a3e8e94b9df17372ae9905f Mon Sep 17 00:00:00 2001
From: Hojun-Cho <ghwns6743@gmail.com>
Date: Wed, 27 Nov 2024 22:56:59 +0900
Subject: [PATCH] add readme

---
 README.md   | 35 ++++++++++++++++++++++++++++++++++-
 boot/boot.c |  1 -
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 24365d0..cab91ae 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,35 @@
-### MBR bootloader
+# FAT16 bootloader
+	x86 FAT16 bootloader
+	
+### How to run
+	1. install image to device
+		install to device
+			./install.sh /dev/sda
+		create image and install
+			./install.sh
+	2. run with qemu
+		qemu-systme-i386 [device | ./build/img]
 
+### Disk layout
+	0x0000 ~ 0x0200: "mbr"
+	0x8000 ~ *     : Using FAT16 filesystem
+	0x8000 ~ 0x8200: "biosboot"
+	    exist "boot" somewhere in FAT16 
+
+### How to work
+	mbr
+		1. bios take us to 0x7C00
+		2. relocate 0x7c00~0x7DFF to 0x7A00~0x7BFF
+		3. load "biosboot" to 0x7C00~0x7DFF
+		4. jump to 0x7c00 => biosboot
+	biosboot
+		1. find "boot" file in FAT16 file sysytem
+		2. load "boot" to 0x40000
+		2-1. 0x40000 ~ 0x401ff: ELF information
+			 0x40120 ~ *      : text, data, bss section 
+		3. jump to 0x40120 => boot
+	boot
+		1. set Global Descriptor Table
+		2. enter protected mode
+		2. set Interrupt Descriptor Table
+		3. call boot function 
\ No newline at end of file
diff --git a/boot/boot.c b/boot/boot.c
index 5106edb..9aa970e 100644
--- a/boot/boot.c
+++ b/boot/boot.c
@@ -60,7 +60,6 @@ wr8(u8 c, u8 fg, u8 bg, int x, int y)
      *where = c | (attrib << 8);
 }
 
-
 void
 boot(dev_t bootdev)
 {